Roller blinds are common forms of window coverings that are used to limit light intrusion, for privacy purposes, to aid in insulating, and to generally enhance the esthetics of a window. Typically, roller blinds have a clutch mechanism at one end that drives a roller tube onto which blind fabric or material is wound or unwound. Commonly the clutch is operated through pulling on one end of a looped chain or cord that is received around a clutch drive sprocket. In many instances the exterior of the clutch includes a cover which serves the purpose of helping to obscure the clutch drive sprocket and much of the internal mechanisms of the clutch in order to present a sleek and generally more pleasing appearance. The clutch cover also commonly includes a chain or cord guide. The chain guide serves to direct or “guide” the chain or cord about the drive sprocket so as to help retain the chain or cord in position, and also to help prevent objects from becoming entangled or interfering with the operation of the drive sprocket. Roller blind clutch chain guides also in many instances contain structures that help to direct the chain or cord downwardly and away from the sprocket for accessing by an operator.
For ease of manufacture, and to help minimize costs, clutch chain guides have traditionally been formed together with the clutch barrel as a unitary part. In such instances the clutch barrel extends from one side of the cover with the opposite side of the cover incorporating hooks or other mechanisms to enable the clutch to be secured to an end bracket of the roller blind. Construction of the clutch cover, chain guide, clutch barrel, and the hooks or fastening mechanisms used to secure the clutch to the end bracket as a unitary component also helps to assist in the transference of rotational torque, that may be applied by operation of the clutch, through the barrel to the cover and ultimately to the end bracket.
Unfortunately, the above form of clutch cover allows the chain guide to orient the chain or cord in only a single manner when the clutch cover or chain guide is secured to the end bracket. In the case of a single blind, that limitation does not usually present concern. However, more recently the use of a dual blind shade, having two roller blinds mounted within one set of end brackets, has become more common. In such cases, it may be desirable for the chain or cord of one of the blinds to be directed outwardly and away from the cord or chain of the other blind held within the same pair of end brackets in order to help reduce tangling or contact between the two sets of chains or cords. Current clutch covers do not readily permit an off-setting of the chains or cords in a dual blind situation.
To account for the heat and frictional forces to which the clutch may be subjected during operation, the clutch barrel must typically be formed from a relatively strong material capable of functioning at elevated temperatures. Such materials often tend to be somewhat brittle, meaning that the barrel and clutch cover/chain guide can break should the roller blind be dropped during or prior to installation. In addition, it is generally desirable for the entire roller blind to be as silent as possible during operation. Contact between the chain or cord and the chain guide during operation of the clutch can cause undesirable noise. Where the chain guide, clutch cover and the clutch barrel are of unitary construction, the chain guide and cover will be of the same, relatively strong, thermally tolerant, material, from which the barrel is made, which in many instances can result in the generation of significant noise through contact with the chain or cord.